1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a transflective liquid crystal display device with different color filter thickness.
2. Description of the Related Art
Liquid crystal display (LCD) devices are widely used as displays in electronic devices such as portable computers, PDAs and cell phones. Liquid crystal display devices are classified into two types. One is transmissive type, and the other is reflective type. The former utilizes the backlight as the light source and the latter utilizes the ambient light. It is difficult to decrease the power consumption for the transmissive LCD due to the power requirements of the backlight. As for the reflective LCD, it has the advantage of power-saving under bright ambient light; unfortunately, it has a limit to show images under dark ambient light.
In order to overcome the drawbacks of these two types of LCDs, a transflective LCD is disclosed. It is capable to show images in not only transmissive mode but also reflective mode. Under bright ambient light, the backlight can be turned off, so the power consumption of the transflective LCD is lower than that of the transmissive LCD. Besides, under dark ambient light, the backlight can be turned on, so the image quality of the transflective LCD is better than that of the reflective LCD.
FIG. 1, a sectional view of a conventional transflective LCD device, helps to illustrate the operation of such devices. As shown in FIG. 1, the conventional transflective LCD device includes a lower substrate 100 (also referred to as an array substrate), an upper substrate 160 and an interposed liquid crystal layer 130. A common electrode 140 and a color filter 150 are formed on the upper substrate 160. An insulating layer 110 and a reflective electrode 120 are formed on the lower substrate 100, wherein the reflective electrode 120 has an opaque portion 122 and a transparent portion 124. The opaque portion 122 of the reflective electrode 120 can be an aluminum layer and the transparent portion 124 of the reflective electrode 120 can be an ITO (indium tin oxide) layer. The opaque portion 122 reflects the ambient light 170, while the transparent portion 124 transmits light 180 from the backlight device (not shown). The liquid crystal layer 130 includes a plurality of spherical spacers (not shown) used to keep a fixed layer thickness or cell gap of the liquid crystal layer 130. Therefore, the transflective LCD device is capable to display in both a reflective mode and a transmissive mode.
Referring to FIG. 1, the backlight 180 penetrates the transmissive portion 124 and passes through the color filter 150 once, and the ambient light 170 reflects the light by the reflective portion 122 and passes through the color filter 150 twice. This leads to different chromaticity in the reflective and transmissive regions. U.S. Publication No. 2002/0003596A1 discloses a method of forming color filters having various thicknesses on the upper substrate, for solving the color purity issue. However, this conventional method requires additional steps to fabricate the color filters and it encounters the difficulty of assembly with lower substrate